ABSTRACT
Protein kinases and their endogenous substrates from the crude cytosolic extract of Saccharomyces cerevisiae were coeluted in the fraction 13 on DE-52 column chromatography. Analyses of SDS-polyacrylamide gel electrophoresis and autoradiography revealed that the peptides between 14 and 34 kDa were the major phosphorylated substrates. In the presence of Ca2+ and Mg2+, the phosphorylation was suppressed strongly by the regulatory subunit of cAMP-dependent protein kinase and slightly by oleic acid, whereas it was augmented appreciably by phosphatidylglycerol (dioleoyl) and phosphatidylinositol.
Subject(s)
Phosphatidylglycerols/metabolism , Phosphatidylinositols/metabolism , Protein Kinases/metabolism , Saccharomyces cerevisiae/metabolism , Adenosine Triphosphate/metabolism , Cyclic AMP-Dependent Protein Kinases/metabolism , Cytosol/metabolism , Electrophoresis, Polyacrylamide Gel , Kinetics , Molecular Weight , Oleic Acid , Oleic Acids/pharmacology , Phosphoproteins/isolation & purification , Phosphoproteins/metabolism , Phosphorylation , Protein Kinases/isolation & purificationABSTRACT
The effects of various agents on the cleavage of serum albumin, interferon, immunoglobulin and complement component C1q by the extracellular protease from Staphylococcus aureus were analysed by SDS-polyacrylamide gel electrophoresis. Arachidonic acid moderately stimulated the proteolysis of serum albumin, interferon and complement component. Phosphatidic acid effectively enhanced the proteolysis of serum albumin and IgG, whereas it inhibited the cleavage of IgM. The proteolysis of IgG was appreciably enhanced by sphingosine. In contrast, phosphatidyl choline and phosphatidyl glycerol were shown to have an inhibitory effect on the proteolysis of IgG and IgM. Phosphatidyl serine, phosphatidyl inositol and phosphatidyl ethanolamine also inhibited the proteolysis of IgG. The failure of any of these agents to exert a persistent effect on the cleavage of all substrates, revealed the complexity of the interactions among the agent, the substrate and the protease.
Subject(s)
Endopeptidases/metabolism , Staphylococcus aureus/pathogenicity , Complement C1q/metabolism , Dose-Response Relationship, Drug , Endopeptidases/drug effects , Immunoglobulins/metabolism , Interferons/metabolism , Phosphatidylcholines/pharmacology , Phosphatidylethanolamines/pharmacology , Phosphatidylserines/pharmacology , Serum Albumin, Bovine/metabolism , Staphylococcus aureus/metabolismABSTRACT
Limited proteolysis by venoms was analysed by the cleaved peptide band(s) in SDS-polyacrylamide gel electrophoresis. The venom from Crotalus atrox degraded interferon, interleukin-2, IgG, IgM, and a crude form of acetyl cholinesterase but had no effect on IgA. Although the venom from Androctonus australis did not exert appreciable proteolysis on any of the immunoglobulins it had potent proteolytic activities against interferon and interleukin-2. The venom from Vespula maculifrons had only a minor proteolytic effect on interferon. The proteolysis by venoms was not effectively inhibited by alpha 1-antitrypsin or a2-macroglobulin. Moreover, no appreciable proteolytic activity was detected in the venoms from Bufo arenarum, Apis mellifera and Heloderma suspectrum.
